Generally, bicycles may be attached to a vehicle rack structure by means of the bicycle frame, wheels, or a combination thereof. Frame attachment may be secure, but the rigidity of a bicycle frame may result in the transfer of potentially damaging forces from the vehicle to the bicycle, for example while driving the vehicle. As a result, the frame may be structurally damaged or misaligned. In addition, points of engagement on the frame may become cosmetically damaged, such as by being dented or scratched. Bicycle tires have an inherent shock-absorbing ability, which may reduce the effect of sudden vehicle motions on a bicycle attached to a rack via one or more wheels.
Vehicle rack structures for attachment to the rear of a vehicle generally incorporate components to receive the front and rear wheels of a bicycle, which generally engage the bottom and/or outer curve of the wheels. As such, the racks of this configuration are typically as long as the bicycle itself, requiring a long and often heavy structure for each bicycle. Additionally, even if such racks are designed to accommodate bicycles of different frame configurations and/or sizes, such as by means of adjustable wheel engaging components and/or stabilizing members that attach to the frame or wheels, vehicle rack structures are generally required to be designed to accommodate the largest of a range of bicycle sizes, resulting in excess structure and bulkiness when the rack is used with smaller-sized bicycles.